A case-control study has been proposed to test the hypothesis that use of menopausal estrogens offers relative protection against the development of large bowel cancer. All 35-74 year old female residents of King and Pierce Counties (Washington) who are diagnosed as having large bowel cancer during an 18-month period are to be interviewed concerning exogenous hormone exposure and menstrual and reproduction experience. Their responses will be compared to those of healthy women randomly selected from the population of these same counties.